1. Field of the Invention
The present invention relates to photometers such as pulse oximeters. More particularly, the invention relates to a pulse oximeter having a low power drive for efficiently powering the light source of the oximeter.
2. Description of the Prior Art
Oximeters are used to measure the oxygenated fraction of hemoglobin in blood by analyzing the absorption of light transmitted through or reflected from the blood. A typical oximeter includes a light source such as a light emitting diode (LED) that generates and directs light toward a sample, a drive circuit for powering the LED, and a detection circuit that detects and analyzes the light from the LED after it has passed through the sample. After the LED is turned on, the detection circuit must "settle" before an accurate reading can be made. This results in inefficient power usage in existing oximeters because power delivered to the LED is wasted while the detection circuit is settling and because much of the current generated by the LED drive circuitry dissipates in resistive components of the circuitry.